The presence of significant quantities of H.sub.2 S and CO.sub.2 in various "sour" industrial gaseous streams poses a persistant problem. Although various procedures have been developed to remove and recover these contaminants, most such processes are deficient, for a variety of reasons.
In one cyclic method currently attracting attention, the sour gas is contacted, preferably with a solvent-reactant system which comprises a regenerable reactant, to produce solid free sulfur which is recovered either prior or subsequent to regeneration. Suitable reactant materials include polyvalent metallic ions, such as iron, vanadium, copper, manganese, and nickel, and include polyvalent metal chelates. Preferred reactants are coordination complexes in which the polyvalent metals form chelates with specified organic acids.
In yet another type of process, aqueous alkaline solutions are employed to absorb the H.sub.2 S from the gas stream and to convert the absorbed H.sub.2 S to elemental sulfur. In general, this type of process employs an aqueous alkaline solution containing vanadium ions and an anthraquinone disulfonate. This type of process usually requires dilute solutions and low H.sub.2 S loadings, resulting in high circulation rates, large capital investments, and high costs.
One of the reasons for dilute solution use in the latter type of process is the real problem of maintaining sufficient levels of vanadium in solution. Another problem associated with this process is that the solid sulfur produced, if special measures are not taken, may be of poor quality, i.e., it may be finely divided and difficult to separate from the aqueous reactant solution. Finally, the breakdown of the anthraquinone disulfonate represents extra expense, as well as itself representing a disposal problem. The invention seeks to overcome these problems, and provides an efficient and economic process for H.sub.2 S removal.